A voltage regulator is typically used to provide a power source to an integrated circuit (IC). Depending on the functionality of the IC, some components of the IC may require a dedicated voltage regulator. For example, circuits such as phase locked loops (PLL) are sensitive to noise in certain frequency bands and thus require an isolated voltage regulator to minimize noise from other circuits.
FIG. 1A depicts one example of a system having a processor 100 with an isolated voltage regulator 110. The processor power supply 105 delivers power to the processor 100. The external voltage regulator 110 provides a dedicated voltage source to a PLL 120 on the processor chip 100. The external voltage regulator 110 is located on a motherboard and is coupled to the PLL 120 through pins 115 and 116 on the processor chip 100. The external voltage regulator 110 is also coupled to a noise filter comprising inductor 130 and capacitor 140 to isolate noise generated by the external voltage regulator 110 from the processor 100. The inductor 130 and capacitor 140 are located on the motherboard.
Alternatively, a voltage regulator may be placed internal to the processor such as in FIG. 1B. The internal voltage regulator 150 is located on the same processor die 170 as the PLL 160. Processor power supply 175 delivers power to the processor 170. The internal voltage regulator 150 generates power for the PLL 160. While the system of FIG. 1B may help reduce costs by removing the need for packaging pins and noise filters associated with an external voltage regulator, the system of FIG. 1B is incompatible with the one shown in FIG. 1A.